With regard to vehicles in general, and at least to some extent heavy/commercial vehicles such as trucks, buses and the like, there is constantly ongoing research and development with regard to increasing fuel efficiency and reducing exhaust emissions.
This is often at least partly due to growing governmental concern in pollution and air quality, e.g. in urban areas, which has also led to the adoption of various emission standards and rules in many jurisdictions.
These emission standards often consist of requirements that define acceptable limits for exhaust emissions of vehicles being provided with combustion engines. For example, the exhaust levels of e.g. nitric oxides (NOx), hydrocarbons (HC), carbon monoxide (CO) and particles are regulated for most kinds of vehicles in these standards.
The undesired emission of substances can be reduced by reducing fuel consumption and/or through the use of aftertreatment (purifying) of the exhaust gases that results from the combustion process.
Exhaust gases from the combustion engine can, for example be treated through the use of a so-called catalytic process. There exist various kinds of catalytic converters, where different types can be used for different kinds of fuel and/or for treatment of different kinds of substances occurring in the exhaust gas stream. With regard to at least nitric oxides NOx (such as, for example, nitric oxide NO and nitric dioxide NO2, respectively) heavy vehicles often comprises a method where an additive is supplied to the exhaust gas stream. The additive is supplied in order to, usually through the use of a catalytic converter, reduce the presence of nitric oxides NOx to less pollutive substances (mainly nitrogen and water vapor).
One common kind of catalytic converter that is used in NOx reduction, where an additive, oftentimes urea based, is added to the exhaust gas stream, is Selective Catalytic Reduction (SCR) catalytic converters.
In the supplying of an additive it is essential that the amount of additive that is supplied to the exhaust gas stream is not too great or too small. Consequently, it is desirable that the supplied amount of additive corresponds to an expected amount of additive. Further, with regard to the reduction it is also important that the additive consists of an additive of an expected kind.
The chemical composition of an additive can be evaluated, for example, through the use of a quality sensor. When the quality sensor indicates a deviating quality of the additive, and/or broken sensor, regulations may require that vehicle performance restrictive measures are being taken. That is, the driver is induced to ensure that additive of appropriate quality and amount is supplied to the exhaust gas stream.